Electric machine with stator cooling teeth

Abstract

An electrical machine, in particular a rotary current generator for motor vehicles, is proposed which has a housing (13) in which a stator (16) is retained, such that a coolant can flow around the outside of the stator (16) from one of its axial face ends (57) to a circumferential region of the stator (16), defining a flow cross section of the flow course through the stator (16) and the housing (13). The flow course is defined toward the stator by outer stator teeth (62) located on the outer circumference of the stator (16).

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]The invention described and claimed hereinbelow is also described in German Patent Application DE 103 61 864.3 filed on Dec. 30, 2003. This German Patent Application provides the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d).BACKGROUND OF THE INVENTION[0002]From Published German Patent Disclosure DE 44 25 000 A1, an electrical machine embodied as a rotary current generator for motor vehicles is known. This reference describes, among other things, the fact that an air gap may be provided, which is located between a circumferential region of a housing part and the lamination packet of the stator.[0003]The electrical machine of the invention having the characteristics of the main claim, in which among other features it is provided that the flow course is defined toward the stator by outer stator teeth located on the outer circumference of the stator, has the advantage that the cooling area of the stator is markedly inc...

AI Technical Summary

Benefits of technology

[0003]The electrical machine of the invention having the characteristics of the main claim, in which among other features it is provided that the flow course is defined toward the stator by outer stator teeth located on the outer circumference of the stator, has the advantage that the cooling area of the stator is markedly increased as a result, and thus the stator can be cooled better on its outer surface.

[0004]It is especially advantageous if outer teeth, extending outward and axially, which define the outer stator slots in the circumferential direction extend from the yoke. This has the advantage that the yoke is not weakened, but instead its surface area is increased by additional material extending out from the yoke. This improves both the magnetic flux in the stator iron on the one hand and the convention on the other.

[0006]A further improvement in the invention is obtained by providing that a housing part, for instance a bearing plate, adjacent to the stator has a toothed or slotted end face, and housing slots are diametrically opposite the outer stator slots. By this provision, an improved guidance of the flow in the circumferential region, that is, at the interface between stator and bearing plate, is made possible, since because of the toothed or slotted end face, additional conduits or flow possibilities are opened up, and thus the flow resistance in this region drops further. The volumetric flow for the coolant can thus be further increased, and as a result the temperature of the stator drops.

[0006]A further improvement in the invention is obtained by providing that a housing part, for instance a bearing plate, adjacent to the stator has a toothed or slotted end face, and housing slots are diametrically opposite the outer stator slots. By this provision, an improved guidance of the flow in the circumferential region, that is, at the interface between stator and bearing plate, is made possible, since because of the toothed or slotted end face, additional conduits or flow possibilities are opened up, and thus the flow resistance in this region drops further. The volumetric flow for the coolant can thus be further increased, and as a result the temperature of the stator drops.

[0007]For adjusting the desired quantity of cooling air in the region of the contact face between the stator and the housing part, it is provided that the housing slots extend in an annular region of the housing part and also end in that region. In addition, via the design, for instance with regard to the length of these housing slots, the stability of the annular region is also influenced in terms of its vibration properties and thus its vulnerability to breakage. If the housing slots did not end in the annular region, the housing part would be weakened too greatly. It is provided that the housing slots end with a chamfer. This has the advantage that the effective flow cross section is especially large at the transition from the region outside the winding heads of the stator iron or stator to the housing part. As a result, the flow can be guided better. Moreover, the risk that these openings will become soiled and thus plugged up is lessened.

[0006]A further improvement in the invention is obtained by providing that a housing part, for instance a bearing plate, adjacent to the stator has a toothed or slotted end face, and housing slots are diametrically opposite the outer stator slots. By this provision, an improved guidance of the flow in the circumferential region, that is, at the interface between stator and bearing plate, is made possible, since because of the toothed or slotted end face, additional conduits or flow possibilities are opened up, and thus the flow resistance in this region drops further. The volumetric flow for the coolant can thus be further increased, and as a result the temperature of the stator drops.

[0009]For improved flow guidance, it is provided that the continuous annular region extends for at least 20% up to approximately 70% of its total axial length over the stator. Thus the continuous annular region covers a certain length of the stator, or of its outer stator teeth. As a result, the cooling air can flow over the surface of the outer stator teeth longer, and the cooling effect for the stator or stator iron is thus improved.

[0010]The vibration properties of the housing part are furthermore improved by this coverage of the stator.

[0011]For further improvement, it is provided that the housing teeth are wider in the circumferential direction than the outer stator teeth.

[0012]To further optimize the heat transfer or flow properties, it is provided that the outer stator teeth are covered by housing teeth in a first approximation over a radial length of 40% to 70%. In a second approximation, it is provided that this coverage amounts to between 50% to 64%.

Problems solved by technology

If the housing slots did not end in the annular region, the housing part would be weakened too greatly.

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